Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optics Express

Common-signal-induced synchronization in photonic integrated circuits and its application to secure key distribution

Takuma Sasaki, Izumi Kakesu, Yusuke Mitsui, Damien Rontani, Atsushi Uchida, Satoshi Sunada, Kazuyuki Yoshimura, Masanobu Inubushi

Published Oct 11, 2017• 59 citations
Publisher

Abstract

We experimentally achieve common-signal-induced synchronization in two photonic integrated circuits with short external cavities driven by a constant-amplitude random-phase light. The degree of synchronization can be controlled by changing the optical feedback phase of the two photonic integrated circuits. The change in the optical feedback phase leads to a significant redistribution of the spectral energy of optical and RF spectra, which is a unique characteristic of PICs with the short external cavity. The matching of the RF and optical spectra is necessary to achieve synchronization between the two PICs, and stable synchronization can be obtained over an hour in the presence of optical feedback. We succeed in generating information-theoretic secure keys and achieving the final key generation rate of 184 kb/s using the PICs.

DOI
10.1364/oe.25.026029

Related papers

Information-theoretic secure key distribution based on common random-signal induced synchronization in unidirectionally-coupled cascades of semiconductor lasers

Hayato Koizumi, Shinichiro Morikatsu, Hiroki Aida +6 more

It has been proposed that a secure key distribution scheme using correlated random bit sequences can be implemented using common random-signal induced synchronization of semiconductor laser systems. In this scheme it is necessary to use laser systems consisting of multiple cascaded lasers to be secure against a powerful eavesdropper. In this paper, we report the results of an experimental study that demonstrate that the common random-signal induced synchronization is possible in cascaded semiconductor laser systems. We also show that the correlated random bit sequences generated in the synchronized cascaded laser systems can be used to create an information-theoretically secure key between two legitimate users.

Optics Express•Jul 18, 2013•78 citations

Photonic Integrated Circuit for Compact Quantum Key Distribution

Martin Achleitner, Aaron Stadler, Marie-Christine Roehsner +5 more

For the establishment of secure communication as well as a future quantum internet, technologies like Quantum Key Distribution (QKD) must become smaller in size, cost-effective in production and more performant. Since attacks like store-now-decrypt-later are already a threat for sensitive data, research in this area must be pushed towards a higher practicality. In this work we show the feasibility of using a photonic integrated circuit (PIC) for application as a QKD transmitter. The PIC (provided by Eindhoven University of Technology) comprises a ring laser source, a Mach-Zehnder interferometer (MZI) with integrated RF phase modulators used for pulse carving and phase modulation as well as an attenuator section. This indium phosphide (InP) chip enables us to generate the necessary states for a 4-state time-bin-phase BB84 protocol [1] implementation. After characterization of all the photonic components and preliminary testing, we were able to generate a secret key rate of approximately 89kbps for 50MHz signal repetition rate with a QBER of 1.3% (in Z-Basis) in a back-to-back configuration.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 23, 2025•0 citations

Phase Synchronization Dynamics of Two Coupled Lasers for Quantum Random Number Generation

Berta Martínez-Pàmias, Miquel Rudé, Cristina Masoller

We performed an experimental and numerical study of an Indium Phosphide (InP) photonic integrated circuit (PIC) designed for quantum random number generation. We studied the dynamics of two weakly mutually coupled semiconductor lasers, and the transient evolution towards the synchronization of the lasers’ optical phases. By carefully adjusting the parameters of a rate-equation model, the simulated dynamics was found to be in qualitatively good agreement with the experimentally observed time traces. Our results allow us to better understand the transient evolution towards synchronization, and provide a foundation for the optimization of the system for photonic quantum random number generation.

International Conference on Transparent Optical Networks•Jul 6, 2025•0 citations

Phase dynamics of two optically coupled InP lasers in a PIC for quantum random number generation

Berta Martínez-Pàmias, Miquel Rudé, Cristina Masoller

We present an experimental and numerical study of the probability distribution of interference pulses from two InP lasers in a photonic integrated circuit (PIC) operated in gain-switching mode through a square-wave signal that turns them on and off. Without laser coupling, the lasers’ phases are random due to quantum spontaneous emission noise, and their phase difference can be translated into a random intensity and exploited for quantum random number generation (QRNG). We analyze the coupling dynamics that lead to optical phase synchronization. Through a direct comparison between experiments and simulations, we demonstrate a clear correlation between laser coupling and the degradation of the randomness of the lasers’ optical phases, providing a better understanding of the operation and performance of the QRNG device.

EPJ Web of Conferences•Jan 1, 2026•0 citations

Security optimization of synchronization in DFB lasers under constant-amplitude random-phase drive light by reducing drive-response correlation

Yuhe Zhang, Anbang Wang, Junpei Xu +6 more

Common-signal-induced laser synchronization promoted a promising paradigm of high-speed physical key distribution. Constant-amplitude and random-phase (CARP) light was proposed as the common drive signal to enhance security by reducing the correlation between the drive and the laser response in intensity. However, the correlation in light phase is not examined. Here, we numerically reveal that the correlation coefficient of the CARP light phase and the response laser intensity (denoted as CC R- φ D ) can reach a value close to 0.6. Effects of parameters including optical frequency detuning, and modulation depth and noise bandwidth and transparency carrier density for CARP light generation are investigated in detail. By optimizing the optical frequency, modulation depth, and noise bandwidth, respectively, CC R-φD can be reduced to 0.32, 0.18, and 0.10. In the meantime, CC R-φD can be further reduced through secondary optimizing of parameters. CC R-φD can be further reduced by increasing transparent carrier density provided response laser synchronization is achieved. This work gives a new insight about the laser synchronization induced by common CARP light, and also contributes a suggestion of security improvement for physical key distribution based on laser synchronization.

Optics Express•Nov 13, 2023•2 citations

Noise-Rejecting Photonic Integrated Circuit for Robust Quantum Random Number Generation

Peter Raymond Smith, Davide G. Marangon, T. K. Paraiso +2 more

Recent advancements in integrated photonics have shown great promise for the serial production of chip-scale quantum random number generators (QRNG). Considerable progress has been made towards developing fully on-chip QRNGs that exploit the interference of phase-randomized fields from two independent lasers. While a common alternative design, based on a single laser and interferometer, would further improve power consumption and ease of operation, monolithic integration of such a design has thus far faced challenges, including high losses and crosstalk. We solve these key challenges and report fast single-laser interferometric QRNGs integrated onto monolithic chips. By combining on-chip optical amplification with electronic common-mode rejection techniques, our photonic integrated circuits (PICs) stably convert the spontaneous emission phase noise of a diode laser into electronic pulses of high-contrast random intensity at GHz clock rates. Using real-time, hash-function-based randomness extraction, uniformly distributed, truly unpredictable random numbers are generated at a rate of 3 Gbps.

Optical Fiber Communication Conference•Aug 18, 2025•4 citations
We experimentally achieve common-signal-induced synchronization in two photonic integrated circuits with short external cavities driven by a constant-amplitude random-phase light. The degree of synchronization can be controlled by changing the optical feedback phase of the two photonic integrated circuits. The change in the optical feedback phase leads to a significant redistribution of the spectral energy of optical and RF spectra, which is a unique characteristic of PICs with the short external cavity. The matching of the RF and optical spectra is necessary to achieve synchronization between the two PICs, and stable synchronization can be obtained over an hour in the presence of optical feedback. We succeed in generating information-theoretic secure keys and achieving the final key generation rate of 184 kb/s using the PICs.
It has been proposed that a secure key distribution scheme using correlated random bit sequences can be implemented using common random-signal induced synchronization of semiconductor laser systems. In this scheme it is necessary to use laser systems consisting of multiple cascaded lasers to be secure against a powerful eavesdropper. In this paper, we report the results of an experimental study that demonstrate that the common random-signal induced synchronization is possible in cascaded semiconductor laser systems. We also show that the correlated random bit sequences generated in the synchronized cascaded laser systems can be used to create an information-theoretically secure key between two legitimate users.
For the establishment of secure communication as well as a future quantum internet, technologies like Quantum Key Distribution (QKD) must become smaller in size, cost-effective in production and more performant. Since attacks like store-now-decrypt-later are already a threat for sensitive data, research in this area must be pushed towards a higher practicality. In this work we show the feasibility of using a photonic integrated circuit (PIC) for application as a QKD transmitter. The PIC (provided by Eindhoven University of Technology) comprises a ring laser source, a Mach-Zehnder interferometer (MZI) with integrated RF phase modulators used for pulse carving and phase modulation as well as an attenuator section. This indium phosphide (InP) chip enables us to generate the necessary states for a 4-state time-bin-phase BB84 protocol [1] implementation. After characterization of all the photonic components and preliminary testing, we were able to generate a secret key rate of approximately 89kbps for 50MHz signal repetition rate with a QBER of 1.3% (in Z-Basis) in a back-to-back configuration.
We performed an experimental and numerical study of an Indium Phosphide (InP) photonic integrated circuit (PIC) designed for quantum random number generation. We studied the dynamics of two weakly mutually coupled semiconductor lasers, and the transient evolution towards the synchronization of the lasers’ optical phases. By carefully adjusting the parameters of a rate-equation model, the simulated dynamics was found to be in qualitatively good agreement with the experimentally observed time traces. Our results allow us to better understand the transient evolution towards synchronization, and provide a foundation for the optimization of the system for photonic quantum random number generation.
We present an experimental and numerical study of the probability distribution of interference pulses from two InP lasers in a photonic integrated circuit (PIC) operated in gain-switching mode through a square-wave signal that turns them on and off. Without laser coupling, the lasers’ phases are random due to quantum spontaneous emission noise, and their phase difference can be translated into a random intensity and exploited for quantum random number generation (QRNG). We analyze the coupling dynamics that lead to optical phase synchronization. Through a direct comparison between experiments and simulations, we demonstrate a clear correlation between laser coupling and the degradation of the randomness of the lasers’ optical phases, providing a better understanding of the operation and performance of the QRNG device.
Common-signal-induced laser synchronization promoted a promising paradigm of high-speed physical key distribution. Constant-amplitude and random-phase (CARP) light was proposed as the common drive signal to enhance security by reducing the correlation between the drive and the laser response in intensity. However, the correlation in light phase is not examined. Here, we numerically reveal that the correlation coefficient of the CARP light phase and the response laser intensity (denoted as CC R- φ D ) can reach a value close to 0.6. Effects of parameters including optical frequency detuning, and modulation depth and noise bandwidth and transparency carrier density for CARP light generation are investigated in detail. By optimizing the optical frequency, modulation depth, and noise bandwidth, respectively, CC R-φD can be reduced to 0.32, 0.18, and 0.10. In the meantime, CC R-φD can be further reduced through secondary optimizing of parameters. CC R-φD can be further reduced by increasing transparent carrier density provided response laser synchronization is achieved. This work gives a new insight about the laser synchronization induced by common CARP light, and also contributes a suggestion of security improvement for physical key distribution based on laser synchronization.
Recent advancements in integrated photonics have shown great promise for the serial production of chip-scale quantum random number generators (QRNG). Considerable progress has been made towards developing fully on-chip QRNGs that exploit the interference of phase-randomized fields from two independent lasers. While a common alternative design, based on a single laser and interferometer, would further improve power consumption and ease of operation, monolithic integration of such a design has thus far faced challenges, including high losses and crosstalk. We solve these key challenges and report fast single-laser interferometric QRNGs integrated onto monolithic chips. By combining on-chip optical amplification with electronic common-mode rejection techniques, our photonic integrated circuits (PICs) stably convert the spontaneous emission phase noise of a diode laser into electronic pulses of high-contrast random intensity at GHz clock rates. Using real-time, hash-function-based randomness extraction, uniformly distributed, truly unpredictable random numbers are generated at a rate of 3 Gbps.